By means of
the Site Assessment of Tornado Threat (SATT) software, Engineering Analysis Inc. (EAI)
has just completed its annual compilation of the top twenty tornado-prone
states, based on the latest National Weather Service data for tornadic activity from 1950 through 2011.Mississippi retains it ranking as the
most tornado-prone state, followed by Alabama.The top twenty states are as follows:

Rank

State.

ACF (%)

Annual Disturbed Land Area (Acres)

1

Mississippi

0.0753

22605

2

Alabama

0.0679

22051

3

Arkansas

0.0599

19961

4

Oklahoma

0.0572

25138

5

Kansas

0.0496

25971

6

Nebraska

0.0407

20024

7

Iowa

0.0402

14374

8

Indiana

0.0386

8861

9

Tennessee

0.0366

9655

10

Georgia

0.0321

11896

11

Louisiana

0.0321

8949

12

Illinois

0.0297

10565

13

Wisconsin

0.0280

9732

14

Missouri

0.0218

9611

15

Ohio

0.0216

5661

16

North Carolina

0.0208

6484

17

South Carolina

0.0206

3970

18

Kentucky

0.0192

4882

19

Pennsylvania

0.0162

4647

20

Minnesota

0.0160

8152

The Annual
Coverage Fraction (ACF) represents tornado probability based on the average
fraction of land annually disturbed by tornadoes within the boundaries of the
state from 1950 through 2011.This
measure of tornado probability is consistent with the definition given in the FEMA Benefit-Cost Analysis
Reengineering (BCAR) Tornado Safe Room Module Methodology Report.The annual disturbed land area can be obtained by multiplying the ACF by
the area of the state.